As the plasma processing apparatuses of the type described above, the followings are known, for instance:
U.S. Pat. No. 4,401,054 PA1 U.S. Pat. No. 4,492,620 PA1 U.S. Pat. No. 4,450,031 PA1 Japanese Patent Application Laying-Open No. 60-120,525 (Patent Application No. 58-228645)
"Plasma Deposition Apparatus" PA2 "Plasma Deposition Method and Apparatus" PA2 "Ion Shower Apparatus" PA2 "A Reactive Ion Etching Method".
The construction of a typical example of the above-mentioned plasma processing apparatuses is shown in FIG. 2.
In FIG. 2, reference numeral 10 denotes a specimen chamber; 20, a plasma formation chamber; and 30, a microwave supply means.
The specimen chamber 10 has a specimen table 11 on which a specimen (wafer, for instance) 40 is mounted and is communicated through gas holes 12 with an exhaust passage 13.
The plasma formation chamber 20 is communicated with the specimen chamber 10 through a plasma extracting orifice 21 on the side opposite the gas holes 12 and a first gas is introduced into the chamber 20 through a first gas introduction system or pipe 22 from a first gas source outside of the chamber 20. An annular pipe 23 having a plurality of small holes is disposed in the vicinity of the outside portion of the orifice 21, so that a second gas is introduced from a second gas source through a second gas introduction system or pipe 24 into the specimen chamber 10. A cooling ring portion 25 surrounds the chamber 20 and a coolant such as water is supplied to the cooling ring portion 25 through a cooling pipe 26 from a coolant source.
A microwave introducing window 27, which is, for instance, made of a silica glass plate is disposed on the end wall of the plasma formation chamber 20 on the side opposite the orifice 21. The microwave from the microwave supply means 30 is introduced into the plasma formation chamber 20 through the window 27, so that the first gas introduced into the chamber 20 through the gas introduction pipe 22 is formed into the plasma.
The microwave supply means 30 comprises a microwave source 31 such as a magnetron which generates microwave having a frequency of, for instance, 2.45 GHz, rectangular waveguides 32 and 33 for propagating the microwave from the microwave source 31 toward the window 27 and a matching tuner 34 interposed between the waveguides 32 and 33. In this case, the microwave is propagated in the TE mode into the plasma formation chamber 20 through the microwave introduction window 27. Thus, the microwave propagated through the introducing window 27 from the rectangular waveguide 33 excites the first gas introduced into the plasma formation chamber 20 to form the plasma.
Electromagnetic coils 50 are disposed to surround the plasma formation chamber 20 in such a way that the plasma of the first gas formed by the electron cyclotron resonance of the introduced microwave is introduced into the specimen chamber 10 through the plasma extracting orifice 21.
The conventional plasma processing apparatus has in general the construction just described above.
In the case of the plasma processing apparatus of the type described above, the specimens 40 which are mounted on the specimen table 11 are effectively processed by the plasma thus produced, so that the plasma etching or deposition can be accomplished.
The plasma processing apparatus of the type utilizing plasma formed by the electron cyclotron resonance (ECR) has a variety of features. When they are applied to CVD, various thin films such as SiO.sub.2, Si.sub.3 N.sub.4 and so on which have a high degree of density and also a high quality can be manufactured at a low temperature without heating and furthermore the damages to the substrate can be minimized. In the application to an etching process, the plasma processing apparatus has features of a high accuracy, a high selection ratio and minimum damage, so that the apparatus is essential in the case of the future fabrication of VLSI circuits.
In the case of the above-described conventional plasma processing apparatus, however, the microwave which excites the gas introduced into the plasma formation chamber 20 is in the TE mode, so that the reflection of the microwave from the plasma formation chamber 20 is high. Consequently, the plasma formation becomes unstable and therefore there was the problem that the first gas cannot be excited effectively.
In addition, the conventional plasma processing apparatus is basically so designed and constructed to process specimens one by one. Therefore, the throughput characteristics such as a processing rate and so on are not sufficient and accordingly there has been a great demand for improving these characteristics. In other words, it is required that an intensity of plasma and an ion current density be increased without deteriorating other advantages.